2 Drums, but sands with one at a time

[Alan Schaffter]

I wonder if something could be rigged up with belts and pulleys that would disengage one drum at a time so it just freewheels. Kind of like an A/C clutch on a car.

I'm fairly certain an A/C clutch would work though I don't know anything about the ratings of those and if they would handle the considerable load placed on them. It would be easy to get a clutch from a junkyard to test without doing an other mods.

The one key feature I would lose is the ability to easily fine tune the parallelism and heights of the drums, unless the machine already had those features. With my setup both of those things can be done quickly and easily on each drum individually using only a box wrench.

Here is a very rough sketch of what I have in mind. It is missing some structure, like the conveyor/conveyor table, teeter totter mounting bracket, pneumatic actuators, etc. but it gives you an idea what I have in mind.

The adjustable pivot stops (red in the diagram) can just be hex bolts. They allow the parallelism and height of each drum to be adjusted individually. Once the parallelism (to the table) has been set for each drum the heights (for the selected grits) for each drum can also be set independently by adjusting both near side and far side stops (not visible) by the same whole number and fractional rotations. The drum height could also be set by ganging the near and far hex bolts together so they turn simultaneously once the drums are parallel.

[Dennis Ripoli]

I see what you mean. Looks pretty simple in the drawing but I'm sure it's going to be pretty complicated and labour intensive to design and build. What do you think of the freewheeling drum Idea? I was thinking about it some more and it would be pretty easy to add a second motor and have seperate motors drive each drum. Maybe using idler pulleys controlled by a lever or actuator to engage each belt as needed.

[James Lord]

I have the Woodmaster 3875- X2 38 inch Double drum sander. It works great. The second drum can be fine tuned to the first drum. So it can apply more or less pressure.

http://www.woodmastertools.com/NS/ac...il.cfm?PID=808

[Alan Schaffter]

I see what you mean. Looks pretty simple in the drawing but I'm sure it's going to be pretty complicated and labor intensive to design and build. What do you think of the freewheeling drum Idea? I was thinking about it some more and it would be pretty easy to add a second motor and have separate motors drive each drum. Maybe using idler pulleys controlled by a lever or actuator to engage each belt as needed.

If you have 16"" or longer drums, you'd need another 3 - 5 hp motor. Now you are talking a BIG extra expense! You can still use one motor with my setup or your electric clutch:



A centered idler can be added between the pulleys to get more belt wrap.

You don't want anything that will cause drag on the inactive drum like a direct or belt drive, but un-powered motor, that includes an idler type clutch- you still get belt drag on the pulleys. Also, if both drums contact the stock and the outfeed drum is inactive, it could act somewhat like a pressure roller, packing dust into the stock.

After looking at my diagram again, I realized once the near side and far side stops are adjusted so the leading drum is parallel to the table, there is no need to adjust the height of that drum further- table elevation takes care of that. The trailing drum only needs micro height adjustment, like retail drum sanders that already have it.

I also plan to add a rotating dust brush just after the outfeed drum to sweep any dust that the DC didn't pick up (happens often) off the top of the board and back into the machine.

[Dennis Ripoli]

I have the smaller 16" G1079 version and can pick up a used 2hp motor for around $100. I'm just bouncing ideas around without making things too complicated but I see your point. I guess your going to build some type of carriage for the drums but how are you going to deal with the center pressure roller being located at the pivot point?

[Alan Schaffter]

I have the smaller 16" G1079 version and can pick up a used 2hp motor for around $100. I'm just bouncing ideas around without making things too complicated but I see your point. I guess your going to build some type of carriage for the drums but how are you going to deal with the center pressure roller being located at the pivot point?

The pivot pin doesn't need to go from side to side- two separate pins. The center will be open for a pressure roller.

[Dennis Ripoli]

Alan, do your drums spin in the same direction as the feedbelt like a climb cut? I wonder if there would be any advantages to reversing the motor direction so it makes a shearing cut instead? Forgive all my questions but I just got this thing and have never used one before.

[Joe Spear]

Those radial arm saw things were still available in 2006 when I got one. You are more ambitious than me, though. I ended up just buying the feeder and tripod stand that were also available when I figured putting it on a radial arm saw was more trouble than it was worth.

[Alan Schaffter]

Alan, do your drums spin in the same direction as the feedbelt like a climb cut? I wonder if there would be any advantages to reversing the motor direction so it makes a shearing cut instead? Forgive all my questions but I just got this thing and have never used one before.

My drums spin in the same direction as the feed belt. I'm sure anything is to be gained by reversing the drums except possibly reducing the amount of dust left on the boards, likewise, rotating in the direction of the drums puts less strain on the conveyor motor. That may not be much of an issue- my feed motor is 1/4 HP Baldor DC gear motor so output torque is pretty substantial. There seems to be no standard among manufacturers- some spin in the feed direction; some the opposite.